含并行连结的网络 GoogLeNet
在GoogleNet出现值前,流行的网络结构使用的卷积核从1×1到11×11,卷积核的选择并没有太多的原因。GoogLeNet的提出,说明有时候使用多个不同大小的卷积核组合是有利的。
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import torch from torch import nn from torch.nn import functional as F |
1. Inception块
Inception块是 GoogLeNet 的基本组成单元。Inception 块由四条并行的路径组成,每个路径使用不同大小的卷积核:
路径1:使用 1×1 卷积层;
路径2:先对输出执行 1×1 卷积层,来减少通道数,降低模型复杂性,然后接 3×3 卷积层;
路径3:先对输出执行 1×1 卷积层,然后接 5×5 卷积层;
路径4:使用 3×3 最大汇聚层,然后使用 1×1 卷积层;
在各自路径中使用合适的 padding ,使得各个路径的输出拥有相同的高和宽,然后将每条路径的输出在通道维度上做连结,作为 Inception 块的最终输出.
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class Inception(nn.Module): def __init__( self , in_channels, out_channels): super (Inception, self ).__init__() # 路径1 c1, c2, c3, c4 = out_channels self .route1_1 = nn.Conv2d(in_channels, c1, kernel_size = 1 ) # 路径2 self .route2_1 = nn.Conv2d(in_channels, c2[ 0 ], kernel_size = 1 ) self .route2_2 = nn.Conv2d(c2[ 0 ], c2[ 1 ], kernel_size = 3 , padding = 1 ) # 路径3 self .route3_1 = nn.Conv2d(in_channels, c3[ 0 ], kernel_size = 1 ) self .route3_2 = nn.Conv2d(c3[ 0 ], c3[ 1 ], kernel_size = 5 , padding = 2 ) # 路径4 self .route4_1 = nn.MaxPool2d(kernel_size = 3 , stride = 1 , padding = 1 ) self .route4_2 = nn.Conv2d(in_channels, c4, kernel_size = 1 ) def forward( self , x): x1 = F.relu( self .route1_1(x)) x2 = F.relu( self .route2_2(F.relu( self .route2_1(x)))) x3 = F.relu( self .route3_2(F.relu( self .route3_1(x)))) x4 = F.relu( self .route4_2( self .route4_1(x))) return torch.cat((x1, x2, x3, x4), dim = 1 ) |
2. 构造 GoogLeNet 网络
顺序定义 GoogLeNet 的模块。
第一个模块,顺序使用三个卷积层。
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# 模型的第一个模块 b1 = nn.Sequential( nn.Conv2d( 1 , 64 , kernel_size = 7 , stride = 2 , padding = 3 ,), nn.ReLU(), nn.MaxPool2d(kernel_size = 3 , stride = 2 , padding = 1 ), nn.Conv2d( 64 , 64 , kernel_size = 1 ), nn.ReLU(), nn.Conv2d( 64 , 192 , kernel_size = 3 , padding = 1 ), nn.ReLU(), nn.MaxPool2d(kernel_size = 3 , stride = 2 , padding = 1 ) ) |
第二个模块,使用两个Inception模块。
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# Inception组成的第二个模块 b2 = nn.Sequential( Inception( 192 , ( 64 , ( 96 , 128 ), ( 16 , 32 ), 32 )), Inception( 256 , ( 128 , ( 128 , 192 ), ( 32 , 96 ), 64 )), nn.MaxPool2d(kernel_size = 3 , stride = 2 , padding = 1 ) ) |
第三个模块,串联五个Inception模块。
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# Inception组成的第三个模块 b3 = nn.Sequential( Inception( 480 , ( 192 , ( 96 , 208 ), ( 16 , 48 ), 64 )), Inception( 512 , ( 160 , ( 112 , 224 ), ( 24 , 64 ), 64 )), Inception( 512 , ( 128 , ( 128 , 256 ), ( 24 , 64 ), 64 )), Inception( 512 , ( 112 , ( 144 , 288 ), ( 32 , 64 ), 64 )), Inception( 528 , ( 256 , ( 160 , 320 ), ( 32 , 128 ), 128 )), nn.MaxPool2d(kernel_size = 3 , stride = 2 , padding = 1 ) ) |
第四个模块,传来两个Inception模块。
GoogLeNet使用 avg pooling layer 代替了 fully-connected layer。一方面降低了维度,另一方面也可以视为对低层特征的组合。
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# Inception组成的第四个模块 b4 = nn.Sequential( Inception( 832 , ( 256 , ( 160 , 320 ), ( 32 , 128 ), 128 )), Inception( 832 , ( 384 , ( 192 , 384 ), ( 48 , 128 ), 128 )), nn.AdaptiveAvgPool2d(( 1 , 1 )), nn.Flatten() ) |
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net = nn.Sequential(b1, b2, b3, b4, nn.Linear( 1024 , 10 )) x = torch.randn( 1 , 1 , 96 , 96 ) for layer in net: x = layer(x) print (layer.__class__.__name__, "output shape: " , x.shape) |
输出:
Sequential output shape: torch.Size([1, 192, 28, 28])
Sequential output shape: torch.Size([1, 480, 14, 14])
Sequential output shape: torch.Size([1, 832, 7, 7])
Sequential output shape: torch.Size([1, 1024])
Linear output shape: torch.Size([1, 10])
3. FashionMNIST训练测试
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def load_datasets_Cifar10(batch_size, resize = None ): trans = [transforms.ToTensor()] if resize: transform = trans.insert( 0 , transforms.Resize(resize)) trans = transforms.Compose(trans) train_data = torchvision.datasets.CIFAR10(root = "../data" , train = True , transform = trans, download = True ) test_data = torchvision.datasets.CIFAR10(root = "../data" , train = False , transform = trans, download = True ) print ( "Cifar10 下载完成..." ) return (torch.utils.data.DataLoader(train_data, batch_size, shuffle = True ), torch.utils.data.DataLoader(test_data, batch_size, shuffle = False )) def load_datasets_FashionMNIST(batch_size, resize = None ): trans = [transforms.ToTensor()] if resize: transform = trans.insert( 0 , transforms.Resize(resize)) trans = transforms.Compose(trans) train_data = torchvision.datasets.FashionMNIST(root = "../data" , train = True , transform = trans, download = True ) test_data = torchvision.datasets.FashionMNIST(root = "../data" , train = False , transform = trans, download = True ) print ( "FashionMNIST 下载完成..." ) return (torch.utils.data.DataLoader(train_data, batch_size, shuffle = True ), torch.utils.data.DataLoader(test_data, batch_size, shuffle = False )) def load_datasets(dataset, batch_size, resize): if dataset = = "Cifar10" : return load_datasets_Cifar10(batch_size, resize = resize) else : return load_datasets_FashionMNIST(batch_size, resize = resize) train_iter, test_iter = load_datasets("", 128 , 96 ) # Cifar10 |
训练结果:
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原文链接:https://blog.csdn.net/weixin_43276033/article/details/124545743